> On 1/7/20 11:08 AM, Jan Hubicka wrote: > > > On 1/6/20 8:03 PM, Jan Hubicka wrote: > > > > > > > OK > > > > > > Actually I am not so sure about this patch - how do we ensure > > > > > > reproducibility in this case? > > > > > ISTM that anyone trying to have reproducible builds shouldn't be using > > > > > PGO based optimizations. > > > > > > > > OpenSUSE does that. Builds are supposed to be reproducible + PGO is used > > > > for number of core packages (like GCC itself). This was motivation of > > > > original Martin's change to drop TOPN values from profile more > > > > agressively. > > > > > > I agree with Honza that we should provide as reproducible builds as > > > possible. > > > On the other hand, we should not be rigid and allow a reasonable sample > > > loss. > > > That's why I added a parameter that be tweaked at openSUSE side. > > > > > > Note that original motivation for the patch was your PR :) So that I'm > > > surprised > > > I don't like the patch much. > > > > I know. However I wonder if this can be done in reproducible way. > > My patch deals with TOP N counters for which we expect quite a high > frequency to trigger an optimization. That said, such values should > not be put out of a TOP N counter. > > > Problem is that small values from profile run polutes the on-disk > > counter and eventually renders it invalid. > > Considering my patch, how will these small values lead to an invalid counter? > > > If libgcov before meerging > > or streaming dropped alues smaller than TOTAL_COUNT/N from the histogram > > it may be enough to fit in the number of entires? (at least in the > > testcase they seem very dominated by one value). > > This will have probably the same effect as the patch I've suggested.
It will not. If you do that before merging/streaming it will remain reproducible (i.e. no matter what in what order you merge data you will always get same histogram) I may be missing something, but I do not see how you can recover reproducibility from info you stream w/o invalidating the counter at merging time. Honza
